This invention relates to a fixed antenna operable in two frequency bands and, more particularly, to such an antenna for use in a handheld communications device.
In recent years, portable handheld wireless communications devices have become increasingly popular. At the present time, cellular telephones operating in the frequency band of 824 MHz through 896 MHz are the most widespread type of such devices. However, the personal communications system (PCS) operating in the frequency band of 1850 MHz through 1990 MHz is gaining in popularity. Accordingly, equipment suppliers are developing portable handheld radio transceivers which operate in both these frequency bands. Thus, there exists a need for an antenna capable of operating in both of the described frequency bands.
If the center frequencies of the two frequency bands were harmonically related, it would be a relatively simple matter to design an antenna operable for both of the bands. However, for the frequency bands discussed above, where the ratio between the center frequencies of the two bands is in the range between two and three, such a harmonic relationship does not exist. Accordingly, there also exists a need for an antenna operable for two frequency bands which are not harmonically related.
Handheld portable radio transceivers must be designed in accordance with certain human factors considerations. Thus, such a device should be compact and lightweight. It is known to design such a device with a rod (or whip) antenna which is selectively retractable into, or extendable out of, the device case. Frequently, the user wishes to place the transceiver in a pocket or purse, but at the same time keep the transceiver turned on so that a call can be received and the user notified of such receipt. This requires a short antenna. However, a retractable antenna with moving parts increases the cost of the transceiver. Thus, there exists a further need for a short fixed antenna which is operable in two frequency bands which are not harmonically related and which provides performance similar to that of an extendable antenna.